1. Field of the Invention
The present invention relates to a method used in a wireless communication system and related communication device, and more particularly, to a method of handling a location reporting procedure and related communication device.
2. Description of the Prior Art
A long-term evolution (LTE) system supporting the 3rd Generation Partnership Project (3GPP) Rel-8 standard and/or the 3GPP Rel-9 standard are developed by the 3GPP as a successor of the universal mobile telecommunication system (UMTS) for further enhancing performance of the UMTS to satisfy increasing needs of users. The LTE system includes a new radio interface and a new radio network architecture that provides high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes multiple evolved Node-Bs (eNBs) for communicating with multiple user equipments (UEs), and for communicating with a core network including a mobility management entity (MME), a serving gateway, etc., for Non-Access Stratum (NAS) control.
A LTE-advanced (LTE-A) system, as its name implies, is an evolution of the LTE system. The LTE-A system targets faster switching between power states, improves performance at the coverage edge of an eNB, and includes advanced techniques, such as carrier aggregation (CA), coordinated multipoint (CoMP) transmissions/reception, uplink (UL) multiple-input multiple-output (UL-MIMO), etc. For a UE and an eNB to communicate with each other in the LTE-A system, the UE and the eNB must support standards developed for the LTE-A system, such as the 3GPP Rel-10 standard or later versions.
Device-to-device (D2D) communication may be realized, after an initialization (e.g., connection establishment and/or peer discovery) is performed (e.g., assisted by an eNB). Then, two UEs may communicate (e.g., transmitting and/or receiving packets) with each other directly according to the D2D communication, and the eNB does not need to forward the packets transmitted between the communication devices. According to the D2D communication, the UEs may communicate with each other via UL resources (e.g., UL subframes configured by the eNB). In general, the D2D communication may also be seen as a D2D service (i.e., proximity service (ProSe)). In addition, a D2D subframe, D2D transmission, D2D communication and D2D discovery can be termed as a sidelink subframe, sidelink transmission, sidelink communication and sidelink discovery, respectively.
A UE needs to perform a discovery procedure (e.g., evolved packet core (EPC)-level ProSe discovery) which includes a location reporting procedure to perform the proximity service. In certain situations, the location reporting procedure does not need to be completed, e.g., when UEs are unlikely to enter proximity within a time window, and unnecessary overhead is transmitted between network entities if the location reporting procedure is not cancelled. According to the 3GPP standard, the location reporting procedure can only be cancelled by the UE, and flexibility and efficiency of the operation of the D2D communication is thus limited. For example, the UE may not know when the location reporting procedure should be cancelled, or the UE is unable to cancel the location reporting procedure. In addition, a timer included in a proximity request message is used for indicating a time period during which the proximity request message is valid. However, it is not clear how the EPC network can process an expired proximity request message, when the timer expires.
Furthermore, it is unknown how an EPC network can handle an EPC assisted WLAN direct communication, if one of the UEs involving in a ProSe discovery procedure detaches from the EPC network or a timer of the ProSe discovery procedure expires.
Thus, a method for solving the above problems is needed.